Porphyria

What is porphyria?

Porphyria is a group of at least eight diseases caused by abnormalities in the chemical steps that lead to haeme production. Found mostly in the blood, bone marrow, and liver, haeme is a vital molecule for all of the body's organs. Haeme is a component of haemoglobin, the molecule that carries oxygen in the blood.

Genetic changes are related to the following types of porphyria.

• acute intermittent porphyria
• ALAD deficiency porphyria
• congenital erythropoietic porphyria
• erythropoietic protoporphyria
• hepatoerythropoietic porphyria
• hereditary coproporphyria
• porphyria cutanea tarda
• variegate porphyria

The signs and symptoms of porphyria vary among types. Some types of porphyria (called cutaneous porphyrias) cause the skin to become overly sensitive to sunlight. Areas that are exposed to the sun develop redness, blistering, and often scarring. The clinical features of other types of porphyria (called acute porphyrias) affect the nervous system. Appearing quickly and lasting from days to weeks, these signs and symptoms include chest and abdominal pain, emotional and mental disorders, seizures, and muscle weakness. Some porphyrias have a combination of acute symptoms and symptoms that affect the skin.

Environmental factors can strongly influence the occurrence and severity of signs and symptoms in some types of porphyria. Alcohol, smoking, certain drugs, hormones, exposure to sunlight, stress, and dieting or fasting can all trigger the signs and symptoms of the disorder.

How common is porphyria?

The prevalence of this condition is unknown, but probably ranges from 1 in 500 to 50,000 worldwide. Certain types of porphyria are more common in specific populations, such as whites in South Africa and Scandinavians.

What genes are related to porphyria?

Mutations in the ALAD, CPOX, FECH, HMBS, PPOX, UROD, and UROS genes cause porphyria.

Variations of the HFE gene increase the risk of developing porphyria.

The genes responsible for the porphyrias make enzymes that are needed to produce haeme. If a gene mutation disrupts the function of any of these enzymes, the process cannot continue normally. Instead, byproducts of the process (compounds called porphyrins and porphyrin precursors) build up in the body, leading to the signs and symptoms of porphyria.

One type of porphyria, porphyria cutanea tarda, has both genetic and nongenetic causes. Mutations in the HFE gene (which also cause an iron overload disorder called haemochromatosis) increase the risk of developing porphyria cutanea tarda.

How do people inherit porphyria?

Inheritance patterns depend on the type of porphyria. Some forms of the condition are inherited in an autosomal dominant pattern, which means one copy of the altered gene is sufficient to cause the disorder. Other porphyrias are inherited in an autosomal recessive pattern, which means two copies of the gene must be altered for a person to be affected by the condition.

What other names do people use for porphyria?

• Haematoporphyria
• porphyrin disorder